Registering for tax so i can issue invoices: Help! (Warsaw)

Hey, I am an english teacher and i want to start my own business, for which i'll need to issue invoices. up to now this has been done by the various agencies i have been working for, such that i didn't need my own tax number. but i want to get more permanent residence here, and want to make my own business, so will need to get the tax details and residency set up for me. Does anybody know of any agencies that specialise in this sort of thing and could do register me for a reasonable price? id be really grateful if you could help, thanks!!